Circles Without Metallic Contact 299

circuit, without any contact of metals (615, etc.). it
^s^further shown that when a pair of zinc and platinum plates
were excited at one end of the dilute nitro-sulphuric acid (615)^
or solution of potash (619), or even in some cases a solution of
cornirion salt (620), decompositions might be produced at the
other end, of solutions of iodide of potassium (635), protochloride
of tin (636), sulphate of soda, muriatic acid, and nitrate of
silver (641); or of the following bodies in a state of fusion:
nitre, chlorides of silver and lead, and iodide of lead (637, 641);
no metallic contact being allowed in any of the experiments.

1006. I will proceed to mention new cases; and first, those
already referred to, where the actionof a little dilute acid produced
a current passing through the solution of the sulphuret of potas-
sium (819); or green nitrous acid (832), or the solution of potassa
(842); for here no metallic contact was allowed, and chemical
action was the evident and only cause of the currents produced.

1007. On the following page is a table of cases of similar excite-
ment and voltaic action, produced by chemical action without
metallic contact. Each horizontal line contains the four sub-
stances forming a circuit, and they are so arranged as to give
the direction of the current, which was in all cases from left to
right through the bodies as they now stand. All the combi-
nations set down were able to effect decomposition^ and they
are but a few of those which occurred in the course of the
investigation.

tooS.—See next page.

1009. It appears to me probable that any one of the very
numerous combinations which can be made out of the follow-
ing table, by taking one substance from each column and
arranging them in the order in which the columns stand, would
produce a current without metallic contact, and that some of
these currents would be very powerful.

Dilute nitric acid

^ 55 g | | Dilute sulphuric acid

Muriatic acid

Solution of vegetable acids
Iodide of potassium
Iodide of zinc
Solution of salt
Many metallic solutions

Rhodium

Gold

Platinum

Palladium

Silver

Nickel

Copper

Lead

Tin

Zinc

Cadmium

ynd in hand. Without